The technology area covered by the embodiments involves a hierarchical mobile communications system comprising a range of heterogeneous communication subsystems. These includes a communications backbone (referred to herein simply as “backbone”). The backbone is either wired, wireless or a combination of both. Such a backbone may include fiber-optics, Internet infrastructure, Base Transceiver Station (BTS), WiMAX, LTE, or any 3G-4G-5G related (mobile or wireless) communications technologies that connect to the core network. The subsystems further include a set of wireless backhauls (referred to herein simply as “backhaul”), such as clusters of well-connected wireless networks such as (multi-hop) mesh or sensor networks, IEEE 802.11, WiFi direct, IEEE 802.15.4, 6LoWPAN, NFC, M2M, device-to-device, LTE-direct, relay networks, or other 5G related (peer-to-peer or ad hoc wireless) communications technologies as well as an access point (AP). APs represent nodes that are part of the wireless backhaul system and which provide a connection with the communications backbone. The AP may be fixed and trusted (e.g. managed by a network operator), or mobile and untrusted (e.g. opportunistic and free-will). Wireless devices are referred to herein as nodes.
Many heterogeneous network approaches designed to blend backhaul and backbone technologies have in common the principle of cooperation in the sense of adhering to a specific protocol specification, which may, for example, be realised as a channel allocation and/or a data packet routing or offloading protocol as dictated by the regulator, the standard, or the ISP. Backhaul wireless networks (P2P, D2D, relay or mesh networks etc.) may be therefore be classified according to the protocol with which they cooperate as follows:                Coordinated backhaul cooperation: this concerns adherence to a set of rules that govern the manner with which wireless devices participate in wireless backhaul communications.        Self-evolving backhaul cooperation: this concerns the process of allowing each node to decide autonomously the level of its contribution, e.g. by means of a reciprocity-based, credit-based or reputation-based decision-making mechanism.        
One of the problems faced by conventional routing schemes concerns the mechanism that provides a sufficient incentive for collaboration, and that protects against selfish (economically rational) or malicious nodes (free-riders) or unfavourable communication conditions such as the curse of the boundary nodes. From a technical point of view, it is not in a node's interest to forward arriving packets. However, refusal to cooperate will severely degrade the network and even impair the node's own performance. A number of prior-art approaches used to encourage packet-forwarding can be categorised into two general types, Credit-based methods and Reputation-based systems that include community enforcement schemes that, by means of detecting and punishing misbehaving nodes seek to encourage cooperation of the nodes.
Reputation based systems suffer several problems. They do not provide a direct incentive for collaboration. This is unfavourable in highly dynamic conditions in which mobile nodes might change location or even change their identification credentials. They depend on the ability of nodes to monitor peer nodes forwarding packets, and analysing these packets in order to detect an attack.
In typical credit-based approaches, a node receives some credit for forwarding a packet, and such credits are deducted from the original sender (or destination). While in many works the credit mechanism requires tamper-proof hardware, it is also possible to rely on a record of electronic receipts, which a node can use to claim credit from a Credit Clearance Service. Credit is, however, typically paid by the originating sender and not the destination node, to help prevent against flooding attacks, in which rogue senders send packets to the destination repeatedly. However, in the download scenario, in which a node does not spend energy to transmit, the node has no incentive to request data from (and pay) the ad hoc network, if it is possible to request this data directly from the source. Thus, the known credit-based approaches cannot be adapted to the backbone and backhaul system architecture.
In credit-based systems credit may need to be paid to every node that forwards a packet, regardless of whether or not the packet reaches its destination. This gives rise to denial-of-service and collusion attacks. For example, if an intermediate node does not forward the packet, then the sender will still need to pay the previous packet-forwarding nodes. However, this allows a collusion attack in which intermediate nodes fabricate packet-forwarding receipts in order to claim credit for data packets which they have not really forwarded. If, otherwise, credit is only paid when a packet reaches its destination, then nodes will have a reduced incentive to forward a packet in fear that a subsequent node may not forward the packet.
Moreover, in credit-based systems in which a fixed amount of credit needs to be paid to every node that forwards packets malicious intermediate nodes may extend the packet forwarding route, including forwarding packets with a delay, so that more of them receive credit for the sender.